Mechanical drive mechanism with programmable output function

ABSTRACT

A mechanical device for causing the angle of an output shaft to be a desired programmable function of an input shaft angle. The input and output shafts are coupled by a tensioned belt which traverses an intermediate idler pulley. The desired function is provided by cam control of the distance separation between the axis of the input shaft and the idler pulley.

United States Patent [191 Bernstein 1 Jan. 23, 1973 [541 MECHANICALDRIVE MECHANISM 2,212,823 8/1940 Bulk ..74/89.22 WITH PROGRAMMABLEOUTPUT 3,203,270 8/1965 Booth 74/89.22 U CTI 3,273,408 9/1966 Nagel etal. 74/89.22

inventor: Albert Bernstein, Sepulveda, Calif.

Assignee: RCA Corporation Filed: Sept. 29, 1970 Appl. No.: 176,479

US. Cl. ..74/89.22, 74/10.6, 74/89.2 Int. Cl ..Fl6h 27/02 Field ofSearch ..74/89.22, 219, 225, 242.11, 74/242.l3, 242.14, 242.15, 89.21,230.23, 242.1, 10.6, 16.29

References Cited UNITED STATES PATENTS Wistrup ..74/10.6 Schurmann..74/242.ll

FOREIGN PATENTS OR APPLICATIONS 1,072,282 12/1959 Germany ..74/l0.6

Primary Examiner-Milton Kaufman Assistant ExaminerWesley S. Ratliff, Jr.Attorney-Edward .1. Norton [57] ABSTRACT A mechanical device for causingthe angle of an output shaft to be a desired programmable function of aninput shaft angle. The input and output shafts are coupled by atensioned belt which traverses an intermediate idler pulley. The desiredfunction is provided by cam control of the distance separation betweenthe axis of the input shaft and the idler pulley.

7 Claims, 5 Drawing Figures mechanical MECHANICAL DRIVE MECHANISM WITHPROGRAMMABLE OUTPUT FUNCTION This invention relates to a mechanicaldevice for causing an output shaft to assume an angle which is aprogrammable function of the input shaft angle.

The device is useful in, although not limited to, instrument dialapplications such as utilized in communication receivers, and signalgenerators, where incremental errors are normally present at arbitrarypoints in the dial range. With the arrangement of the invention,mechanical corrections may be made at predetermined error points thuseliminating the need for calibration charts. I

The arrangement of the invention is also useful in analog computationapplications for providing linear, non-linear, or arbitrary functions.

The present inventive arrangement is simpler, and less costly thanexisting arrangements, which for example, find it necessary to utilizemechanical differentials, precision gearing and other more complexmeans. The present arrangement is inherently antibacklash, provides highmechanical magnification of the input displacement, offers at least 360operation and is easily adjustable for a desired function.

It is therefore an object to provide an improved arrangement forproviding an output shaft angle rotation which is a programmablefunction of the input shaft angle rotation.

' Briefly according to the invention there is provided a first reel likemeans mounted for rotation about an axis. Cam means are mounted forrotation with the first reel like means. A second reel like means ismounted for rotation about an axis. Guide means is mounted in spacedrelation with the first mentioned axis. Cam follower means are providedin cooperative relation with the cam means. The follower means iscoupled in fixed spaced relation with the guide means for varying thespacing between the first mentioned axis and the guide means accordingto the cam means. A cord like means intercouples the first and secondreel like means and the guide means. And there is provided further meanscoupling the first and second reel like means in a manner to provide acontra-rotational force on the reel means.

FIG. 1(a) and (b) are a plan and side view respectively of oneembodiment of the invention.

FIG. 2 is an exploded view ofa cam arrangement according to theinvention.

FIG. 3 is a further plan view of the embodiment of FIGS. 1(a) and (b)illustrating an operating condition of the embodiment.

FIG. 4 illustrates a plot of a typical function curve obtainableaccording to the invention.

In FIG. 1(a) and (b) an input shaft 2 is rotatably mounted to a supportmember 4 by suitable means such as bushing, sleeve or bearing 6. A firstpulley or reel like member 8 is fixedly mounted on the shaft 2, such asby set screws not shown, for corresponding rotation therewith. A cammember 10 is secured to one side of the member 8 by means such as screws12. The cam surface of member 10 extends annularly about the shaft 2.Details of a preferred embodiment for the cam member 10 will bediscussed hereinafter with regard to FIG. 2.

A cam follower member 14 is arranged in cooperative relation to the cam10. The cam follower I4 is preferably rotatably mounted as shown, bysuitable means such as a bushing, sleeve or bearing, to the arm or rodmember 16. The arm 16 is pivotally mounted at a first end to the supportmember 4 by the pin or rod 18 and a suitable bushing, bearing or sleeve20. In the vicinity of the second end of the arm 16, a pulley or drumlike guide member 22 is mounted to the arm 16. It is preferable that themember 22 be rotatably mounted to the arm 16 however the guide member 22may also be a fixed shaft or rod. As shown, for example,

the guide member 22 is rotatably mounted to the support member 16 bymeans of a shaft 24 and a bearing, bushing or sleeve 26.

In FIG. 1a and lb there is shown a third pulley or reel like member 28having an output shaft 30 affixed to the member 28. The member 28 withits shaft 30 is mounted on the shaft 2, in known manner, to provide freerotation of the member 28 and shaft 30 about the shaft 2. The pulley orreel like member 8 and 28 are intercoupled by a belt or cord like means32, which preferably does not elongate under tension. The means 32 issecured by suitable means at one end to a point 34 on the periphery ofmember 28 and at its other end to point 36 on the periphery of themember 8. As shown the belt or cord means 32 is at least partially.wrapped about the member 28, and extends to and about the spaced pulleymember 22 and then back on to the member 8. It is to be noted howeverthat the means 32 may also be arranged to have one or more wraps aboutthe member 8, 22 and 28.

Also coupling the members 8 and 28 is a resilient means 38. Theresilient member 38 is secured to the respective members 8 and 28 in apre-stressed manner to provide contra-rotational forces on the members 8and 28 and thus maintain tension in the cord like means 32. In theembodiment shown in FIGS. 1(a) and (b), the resilient means 38 is agenerally spiral shaped spring. The spring 38 is disposed between the'members 8 and 28, and extends about the input shaft 2. One end of spring38 is secured to member 28 by means such as a pin 42. The other end ofspring 38 is secured to member 8 by means such as a pin 40.

The cam member 10 of FIG. 1 may for example be arranged as shown in FIG.2, in which like reference numerals refer to and correspond with thoseshown and described with regard to FIG. I. As shown in the exploded viewof FIG. 2 the cam member 10 may be comprised of a plurality of disks 50.Any or all of the disks 50 may be circular, eliptical, irregular, or anygiven shape, such that when secured together the composite periphery ofthe disks 50, provide a desired cam surface. It will be understoodhowever that a single disk with the desired peripheral shape may also beused. The disks 50 each have an aperture 52 for mounting about the shaft2. The apertures 52 are made to be larger than the diameter of the shaft2. The disks 50 also have a plurality of spaced slots or elongatedapertures 54. The slots 54 facilitate mounting of the disks 50, singlyor in a stacked configuration, to the member 8 by means, for example,such as screws 12. The slots 54 provide and are oriented to permitadjustment of the distance of points on the peripheral surface of a disk50 with respect to the longitudinal axis 56 of the shaft 2.

As will be more fully understood from the subsequent discussion of theoperation of the invention, this arrangement provides a simple andefficient means, for establishing or altering the desired outputfunction, in response to a given input shaft angle.

The arrangement of FIG. 3 is the same as that shown and described withregard to FIGS. 1(a) and 1(b), although certain elements are not shownfor clarity. In operation of the invention, as shown in FIG. 3, theresilient means 38 maintains tension on the belt 32 and the input andoutput members 8 and 28 respectively maintain a fixed angularrelationship with respect to one another as long as the cam distance Q,shown in FIG. 3, is constant. For the just described condition, theoutput shaft angle '0 is equal to the input shaft angle a. Modificationof the output angle 8 of the shaft 30 such that it is a non-linearfunction of the input angle a, is provided by the variation of thecenter to center spacing R, between the members 8 and 22 as the shaft 2is rotated. This is accomplished in the manner shown and to be describedwith regard to FIG. 3, wherein the travel of the guide member 22 isshown somewhat exaggerated for purposes of clarity. When the dimensionR, is incrementally changed from R, to R, A by virtue of the input shaft2 rotation a and response of the cam 10 and follower 14 which increasesthe distance Q, the angle of the output shaft 30 moves to a B Thisoccurs because the length of the belt or cord 32, tangent to the members8 and 28, has increased and only the member 28 is free to rotate toaccommodate this length change. As indicated, the modification of thedistance R, to R, A is accomplished by means of the cam 10 and follower14, which cause the arm 16 to rotate through the angle 6 The manner inwhich the cam assembly 10 is secured to the pulley member 8, providestranslational motion a distance along the radial direction R for eachposition of the input shaft angle a Since the cam assembly may be madepreadjustable, as described with regard to FIG. 2, the cam follower 14action provides an output angle correction B which is a function of camheight or distance Q and therefore a desired function of the input anglea The relationship of the correction angle {3 (in radians) to cam heightor distance 0 is defined by the following relationships:

where;

F= Diameter ofthe member 8 E= Diameter of the cam follower l4 C=Diameter of the member 22 Q Cam displacement for input shaft angleDimensions A, R, and R, are as shown in FIG. 3.

If reference is made to FIG. 4, there is shown a plotted curve 60 ofinput angle 0: versus output angle 6 (in radians), for a typicalnon-linear function which may be realized according to the invention.

For purposes of explanation the shafts 2 and 30 have been referred to asinput and output shafts respectively, however it will be understood thatfor a particular application the shaft 30 may be considered the inputshaft with shaft 2 as the output shaft.

It will also be understood that the above described arrangements areonly illustrative of the invention. Other arrangements may be devised,within the spirit and scope of the invention, such as mounting the reellike means for rotation about separate axes, while however maintainingthe indicated desired intercoupled relationship between the input andoutput members.

What is claimed is:

1. Apparatus for establishing relative angular position between at leasttwo rotatable members, comprising:

first reel like means mounted for rotation about an axis; cam meansmounted for rotation with said first means; second reel like meansmounted for rotation about an axis;

guide means mounted in spaced relation to said first mentioned axis;

cam follower means mounted in cooperative relation with said cam means,said follower means coupled in fixed spaced relation with said guidemeans for varying the spacing between said first mentioned axis and saidguide means according to said cam means;

cord like means intercoupling said first and second reel like means andsaid guide means; and

further means coupling said first and second reel like means in a mannerto provide a contra-rotational force on said reel means.

2. The invention according to claim 1, wherein;

said first and second reel like means are mounted coaxially.

3. Apparatus for establishing relative angular position between at leasttwo rotatable members, comprismg:

first reel like means mounted for rotation about an axis;

second reel like means mounted for rotation about an axis;

cam means surrounding said first mentioned axis and mounted for rotationwith said first reel like means;

cam follower means including guide means mounted for movement toward andaway from said first mentioned axis in accordance with said cam means;

cord like means having opposite end portions secured to said first andsecond reel like means and an intermediate portion disposed about saidguide means; and

resilient means coupling said first and second reel likemeans in amanner to provide a contra-rotational force on said reel means.

4. Mechanical positioning apparatus, comprising:

a rotatable shaft including a first pulley and a cam surface mountedabout said shaft for rotation therewith;

a second pulley mounted for rotatable movement about said shaft,

resilient means coupling said first and second pulleys for providing acontra-rotational force between said pulleys;

an arm having a first end pivotally mounted adjacent said shaft;

a guide pulley mounted to the free end of said arm for movement towardand away from said shaft;

cam follower means secured to said arm between said ends in cooperativerelation with said cam surface; and

cord like means having one end secured to said first pulley and saidother end secured to said second pulley, said cord like means extendingat least partially about said first and second pulleys and said guidepulley, the relative angular position of said first and second pulleysbeing determinedby the spacing between said guide pulleys and said shaftthrough said cord means in accordance with said cam surface.

5. The invention according to claim 4, wherein; said resilient meansincludes a spiral spring disposed annularly about said shaft with afirst end secured to said first pulley and the opposite end secured tosaid second pulley.

6. The invention according to claim 5, wherein; said cam surface iscomprised of a plurality of disks each having a desired shapedperiphery, said disks being arranged so that at least a portion of theirperiphery is traversed by said cam follower means when one of said firstand second pulleys is rotated.

7. The invention according to claim 6, wherein; at least one of saidplurality of disks includes a slot for mounting said disk with respectto said shaft, said slot enabling lateral movement of said disk forestablishing a desired spaced relation between the axis of rotation ofsaid shaft and points on the periphery of said disk.

1. Apparatus for establishing relative angular position between at leasttwo rotatable members, comprising: first reel like means mounted forrotation about an axis; cam means mounted for rotation with said firstmeans; second reel like means mounted for rotation about an axis; guidemeans mounted in spaced relation to said first mentioned axis; camfollower means mounted in cooperative relation with said cam means, saidfollower means coupled in fixed spaced relation with said guide meansfor varying the spacing between said first mentioned axis and said guidemeans according to said cam means; cord like means intercoupling saidfirst and second reel lIke means and said guide means; and further meanscoupling said first and second reel like means in a manner to provide acontra-rotational force on said reel means.
 2. The invention accordingto claim 1, wherein; said first and second reel like means are mountedcoaxially.
 3. Apparatus for establishing relative angular positionbetween at least two rotatable members, comprising: first reel likemeans mounted for rotation about an axis; second reel like means mountedfor rotation about an axis; cam means surrounding said first mentionedaxis and mounted for rotation with said first reel like means; camfollower means including guide means mounted for movement toward andaway from said first mentioned axis in accordance with said cam means;cord like means having opposite end portions secured to said first andsecond reel like means and an intermediate portion disposed about saidguide means; and resilient means coupling said first and second reellike means in a manner to provide a contra-rotational force on said reelmeans.
 4. Mechanical positioning apparatus, comprising: a rotatableshaft including a first pulley and a cam surface mounted about saidshaft for rotation therewith; a second pulley mounted for rotatablemovement about said shaft, resilient means coupling said first andsecond pulleys for providing a contra-rotational force between saidpulleys; an arm having a first end pivotally mounted adjacent saidshaft; a guide pulley mounted to the free end of said arm for movementtoward and away from said shaft; cam follower means secured to said armbetween said ends in cooperative relation with said cam surface; andcord like means having one end secured to said first pulley and saidother end secured to said second pulley, said cord like means extendingat least partially about said first and second pulleys and said guidepulley, the relative angular position of said first and second pulleysbeing determined by the spacing between said guide pulleys and saidshaft through said cord means in accordance with said cam surface. 5.The invention according to claim 4, wherein; said resilient meansincludes a spiral spring disposed annularly about said shaft with afirst end secured to said first pulley and the opposite end secured tosaid second pulley.
 6. The invention according to claim 5, wherein; saidcam surface is comprised of a plurality of disks each having a desiredshaped periphery, said disks being arranged so that at least a portionof their periphery is traversed by said cam follower means when one ofsaid first and second pulleys is rotated.
 7. The invention according toclaim 6, wherein; at least one of said plurality of disks includes aslot for mounting said disk with respect to said shaft, said slotenabling lateral movement of said disk for establishing a desired spacedrelation between the axis of rotation of said shaft and points on theperiphery of said disk.